This invention relates to a wireless detonator.
In order for a wireless detonator to be used safely and effectively it must be activated (switched on), immediately before deployment. As a wireless detonator has an on-board energy source, typically a battery, a situation in which battery life can be exceeded before firing of the detonator takes place must be avoided.
In one solution to this problem a detonator has been equipped with a magnetic reed switch which is enabled, using a suitable magnet, at the time the detonator is placed into a blast hole. This approach is, however, not completely satisfactory because a reed switch can be actuated erroneously by a stray magnetic field such as that generated, for example, by a current-carrying conductor.
In a different approach an optical signal is used to enable the battery. This can present technical problems. Another technique requires the battery to be loaded into the detonator immediately before deployment. This can be difficult for account must be taken of the arduous conditions which can prevail in a mining environment.
Apart from these aspects, a wireless detonator is sensitive to power consumption. Communication with the detonator consumes energy which is drawn from the on-board battery source. Communication is slow through rock (when the detonator is installed in a borehole) and a short message can take a long time to be transmitted, during which period energy can continuously be drawn from the battery. At all times care must be taken to ensure that there is adequate energy in the battery to fire an ignition element when required.
An object of the present invention is to address, at least to some extent, the aforementioned factors.